GIS analysis of Rutor Glacier (Aosta Valley, Italy) volume and terminus variation

Glaciers are an important economic and natural resource to beprotected. It is important to develop new techniques for surveying and monitoring glacial bodies that are generally and rapidly retreating due to present climate conditions linked to global warming. Terminus variations in Italian Alpine Glaciers are traditionally determined yearly by measuring the distance between the terminus and ground control points. Thanks to new technologies and digital cartography, it is possible to generate and manage accurate glacier models that can integrate data time series to obtain more detailed views. Variations in the surface area and volume of Rutor Glacier (Val d’Aosta), from its maximum expansion in the Little Ice Age to the present, ongoing retreat, were determined through a combination of ground surveys, digital techniques and pre-existing data time series. From the mid-19th century to 2004 the glacier terminus retreated 2 km, but there is evidence for two different cold periods of glacier advance. Furthermore, the glacial retreat that began again in 1990 seems to be faster than that of previous periods of recession. Rutor Glacier lost about 480 million cubic meters of ice between the Little Ice Age and 1991. Morphologic and volumetric analyses indicate that in the last decades Rutor Glacier has lost large quantities of ice mass with no significant terminus retreat (–46 million cubic meters of ice against - 1.4 hectares of areal extension with respect to the total surface area of 911 hectares); the glacier has gradually thinned while maintaining an almost constant surface area. The Equilibrium Line Altitude changed from 2775 m in the Little Ice Age maximum to 2850 m in 1991, for a total increase of 75 m.